Conventionally, as such a type of a cutting tool, various cutting tools have been proposed in which a flow path is provided within a cutting tool holder (hereinafter, also referred to merely as holder) in order to supply a coolant to a cutting edge of a cutting tip (an cutting insert such as a throw-away tip) in a pouring manner. Such a cutting tool is configured such that an ejection port connected to the flow path is opened near the front end of the holder to supply a coolant (a cutting fluid, etc.) fed under pressure within the flow path, as a high-pressure jet flow toward a rake face etc. forming the cutting edge. Among such cutting tools, there is a technique in which the ejection port is provided in the cutting tool holder (main body) and at the side of a lateral flank forming the cutting edge such that the coolant can be jetted out toward the lateral flank (Patent Document 1, Patent Document 2). In the cutting tool configured such that the coolant is ejected from such an ejection port, in addition to cooling of the cutting edge (knife edge) and a to-be cut object (temperature rise prevention) by the coolant, the effect of lubrication is high, and this configuration is also effective for prevention of flank wear. Moreover, this configuration is effective for treatment of swarf, for example, an effect of blowing swarf at the lateral flank side is also obtained, and thus an effect of preventing swarf from being tangled with the cutting tool or damaging a machined surface is obtained. In the present application, a “lateral flank” regarding the cutting tool holder means a side surface facing in the same direction as a lateral flank of a cutting tip fixed to the holder, and a “rake face” regarding the cutting tool holder means a surface facing in the same direction as a rake face of the cutting tip fixed to the holder.
Incidentally, conventionally, in the case of processing a to-be cut object with high accuracy by turning, a cutting tool 2 should be used at a position that is as close to a spindle head of a lathe or a claw for chucking the to-be cut object as possible. In particular, in precision processing of a to-be cut object (round bar) having a small diameter, this demand is high from the standpoint of prevention of runout. Meanwhile, in the case where a to-be cut object is a predetermined shaft or a pin-like component and is to be efficiently processed, a lathe (automatic lathe) is used which is equipped with an automatic material feed device configured such that a material to be processed (a long bar material) is passed within a rotating hollow spindle (main shaft), and is automatically sent out by a required length each time predetermined processing ends, so that the next processing can be performed. In such a lathe, a plurality of cutting tools (cutting tools for outer diameter processing and groove formation) required for processing the component, which is a to-be cut object, are fixed to a tool rest, for example, above a spindle (rotation shaft) in a comb teeth-like arrangement so as to be spaced apart from each other in a direction perpendicular to the rotation shaft and parallel to each other. Processing is carried out as follows: in accordance with cutting, the tool rest is moved in the perpendicular direction, traversing feed of the tool rest (movement in the radial direction of the rotation shaft (e.g., in the downward direction) is performed for performing cutting with a cutting tool selected per processing, and cross feed (feed in the direction along the rotation shaft) is performed as automatic feed at the material side.
As described above, in turning with the automatic lathe in which cross feed (feed in the direction along the rotation shaft) is performed as automatic feed at the to-be cut object side, the tool rest itself is provided near the front of the spindle head (or the claw of a chuck) in the direction along the rotation shaft, and thus the cutting tools for outer diameter processing and the like are necessarily disposed with a small gap maintained to such an extent as not to interfere with the front of the spindle head. Each cutting tool is mounted on the tool rest such that the lateral flank of the cutting tool holder (shank) forming the cutting tool and a cutting edge corner of a cutting tip provided to the cutting tool are located as close to the spindle head (or the claw of the chuck) as possible. The same applies to the case of using a cutting tool having, at the lateral flank side, an ejection port for ejecting the coolant toward the cutting edge, as in the cutting tool holder of the cutting tool described above.